This invention relates to solvent extraction and particularly, although not exclusively, provides a solvent extraction process and a novel solvent mixture for use in solvent extraction.
Applicant""s co-pending European Patent Application No. 94 301199.9 describes an improved method for the extraction, concentration and preservation of fragrances and flavours using an extraction solvent comprising a non-chlorinated hydrocarbon solvent in the liquid phase. The method is found to selectively extract oils from natural raw materials, for example rose oil from roses.
PCT Patent Publication No. WO 95/26794 (Imperial Chemical Industries Plc) describes a process for extracting a composition comprising a biologically active compound or a precursor thereof from a raw material using an extraction solvent comprising a C1-4 (hydro)fluorocarbon together with a co-solvent selected from dimethyl ether and butane.
Whilst the processes described in the aforementioned documents are advantageous in some circumstances, there is a limit to the types of materials that can be extracted. For example, relatively polar materials cannot be extracted from raw materials.
It is an object of the present invention to address problems associated with the aforementioned processes.
According to a first aspect of the present invention, there is provided a process for the extraction of at least one relatively polar component from a material comprising the steps of:
(a) contacting the material with a solvent mixture comprising a C1 to C4 fluorinated hydrocarbon and a co-solvent having a dielectric constant (at 20xc2x0 C.) of at least 5; and
(b) separating the charged solvent mixture from said material.
Unless otherwise stated herein, an alkyl group may have up to 10, preferably up to 8, more preferably up to 6, especially up to 4 carbon atoms, with methyl and ethyl groups being preferred. Any alkyl group referred to herein may be optionally substituted with one or more substituents which may be selected from halogen atoms, and optionally substituted alkyl, acyl, acetal, hemiacetal, acetalalkyloxy, hemiacetalalkyloxy, nitro, cyano, alkoxy, hydroxy, amino, alkylamino, sulphinyl, alkylsulphinyl, sulphonyl, alkylsulphonyl, sulphonate, amido, alkylamido, alkylcarbonyl, alkoxycarbonyl, halocarbonyl and haloalkyl groups. Preferably, alkyl groups referred to are un-substituted.
The C1 to C4 fluorinated hydrocarbon may be non-chlorinated. Preferably, it comprises one or more carbon, fluorine and hydrogen atoms only. Preferably, said fluorinated hydrocarbon is a C1 to C3, more preferably, a C1 to C2 fluorinated hydrocarbon. Especially preferred is a C2 fluorinated hydrocarbon.
Said fluorinated hydrocarbon may include up to 10, preferably up to 8, more preferably up to 6, especially up to 4, fluorine atoms.
Said fluorinated hydrocarbon is preferably aliphatic. It is preferably saturated.
Said fluorinated hydrocarbon may have a boiling point at atmospheric pressure of less than 20xc2x0 C., preferably less than 10xc2x0 C., more preferably less than 0xc2x0 C., especially less than xe2x88x9210xc2x0 C. The boiling point may be greater than xe2x88x9290xc2x0 C., preferably greater than xe2x88x9270xc2x0 C., more preferably greater than xe2x88x9250xc2x0 C.
A preferred fluorinated hydrocarbon solvent is tetrafluoroethane with 1,1,1,2-tetrafluoroethane being especially preferred.
The dielectric constant of said co-solvent may be at least 6, is preferably at least 15 and is especially at least 20. The dielectric constant may be less than 120, preferably less than 110, more preferably less than 100, especially less than 90.
The boiling point of said co-solvent may be greater than 0xc2x0 C., preferably greater than 25xc2x0 C., more preferably greater than 40xc2x0C., especially greater than 50xc2x0 C. Said boiling point may be less than 250xc2x0 C., preferably less than 215xc2x0 C., more preferably less than 175xc2x0 C., especially less than 150xc2x0 C.
Said solvent mixture may include at least 0.25 wt %, preferably at least 0.5 wt %, more preferably at least 1 wt %, especially at least 2 wt % of said co-solvent. Said solvent mixture may include less than 20 wt %, preferably less than 15 wt %, more preferably less than 10 wt %, of said co-solvent.
Said solvent mixture may include at least 60 wt %, preferably at least 70 wt %, more preferably at least 80 wt %, especially at least 90 wt % of said fluorinated hydrocarbon.
Said solvent mixture preferably comprises a substantially saturated solution of said co-solvent in said fluorinated hydrocarbon.
Said co-solvent may be selected from amides, especially N,Nxe2x80x2-dialkylamides and alkylamides, with dimethylformamide and formamide being preferred; sulphoxides, especially dialkyl sulphoxides, with dimethylsulphoxide being preferred; alcohols, especially aliphatic alcohols for example alkanols, with methanol, ethanol, 1-propanol and 2-propanol being preferred; ketones, especially aliphatic ketones, for example dialkyl ketones, with acetone being especially preferred; organic acids, especially carboxylic acids with formic acid and acetic acid being preferred; carboxylic acid derivatives, for example anhydrides, with acetic anhydride being preferred; cyanide derivatives, for example hydrogen cyanide and alkyl cyanides, with methyl cyanide and liquefied anhydrous hydrogen cyanide being preferred; ammonia; sulphur containing molecules including sulphur dioxide, hydrogen sulphide and carbon disulphide; inorganic acids for example hydrogen halides with liquefied anhydrous hydrogen fluoride, chloride, bromide and iodide being preferred; nitro derivatives, for example nitroalkanes and nitroaryl compounds, with nitromethane and nitrobenzene being especially preferred.
Preferably, said co-solvent is selected from carboxylic acids, carboxylic acid derivatives, especially amides, ketones and alcohols. Said co-solvent may have less than 10, preferably less than 8, more preferably less than 6, especially less than 4 carbon atoms. Said co-solvent is preferably an aliphatic compound.
Said co-solvent is preferably substantially unable to react with said component and/or with said material under the conditions of said process.
Said co-solvent and said C1-4 fluorinated hydrocarbon preferably form a constant boiling mixture or azeotrope.
Said solvent mixture may include a first and second co-solvent each of which may independently have any of the properties or features of said co-solvent referred to hereinabove.
In the method, the charged solvent may be collected by decantation. Alternatively, the charged solvent may be collected by sedimentation. Alternatively, the charged solvent may be collected by filtration.
The method preferably includes the step of removing said solvent mixture from the remainder of said material, after step (b). Removal of said solvent material may be achieved by providing conditions for the evaporation of said solvent. For example, the temperature may be raised, suitably less than 50xc2x0 C., preferably less than 40xc2x0 C., more preferably less than 30xc2x0 C., and/or the pressure may be reduced to less than atmospheric pressure.
As an alternative to evaporating the solvent or in addition thereto, the solvent mixture (including the extract(s)) may be washed with copious amounts of water which may be suitable when the co-solvent(s) have some solubility in water and/or is/are less volatile than the C1-4 fluorinated hydrocarbon. Thus, in this case, the co-solvent(s) may be removed by dissolution in water and, subsequently, the C1-4 fluorinated hydrocarbon may be removed by evaporation as aforesaid. Where washing with water in the manner described does not produce a satisfactory result, for example due to the formation of an emulsion or where the extract itself is also removed in high qualities by dissolution in the water, a salt, for example sodium sulphate or sodium chloride, may be added to the water to suppress the ionisation and solubility of the extracted components.
The process may include additional steps before or after the steps described above. In one embodiment, said material containing said component may be contacted with an alternative solvent or solvent mixture, suitably prior to steps (a) above. Said alternative solvent or solvent mixture preferably is arranged to extract relatively non-polar components and preferably comprises a C1-4 fluorinated hydrocarbon, optionally in combination with one or more co-solvents having a dielectric constant at 20xc2x0 C. of less than 5. Said C1-4 fluorinated hydrocarbon of said alternative solvent or solvent mixture may be as described in any statement herein. Said co-solvent(s) may be as described in WO 95/26794, the contents of which are incorporated herein by reference.
Said material containing said component may be naturally occurring or a synthetic mixture, for example a reaction mixture. Said component may be a pharmaceutical product or an intermediate produced from the fermentation of mycelial or fungal culture or a product from a synthetic chemical reaction. Said component is preferably an active ingredient, for example it may be a pharmaceutical or pesticide, or a pre-cursor thereof.
Said material containing said component is preferably an organic material which is preferably naturally occurring (or at least a pre-cursor thereof is naturally occurring) and/or is of natural origin. Said material is preferably a biomass.
According to a second aspect of the present invention, there is provided a solvent mixture comprising a C1 to C4 fluorinated hydrocarbon and a co-solvent having a dielectric constant (at 20xc2x0 C.) of at least 5.
The invention extends to the use of a solvent mixture as described herein in a solvent extraction process.
Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any other aspect of any invention or embodiment described herein.
The invention will now be described, by way of example.